Chapter 9: Forces and Energy

forces and energy

the 2 types of forces

contact and non-contact forces

contact forces

forces acting between two objects that are in physical contact with eacher other

examples of contact force

friction and elastic forces

friction

the force that opposes motion between two surfaces in contact

elastic forces

the force acting on a stretched or compressed elastic object to return to its original shape

non-contact forces

forces acting on two objects that are not touching each other

examples of non-contact forces

gravitational and magnetic force

gravitational force

the force that attracts two objects with mass towards each other

magnetic forces

the force exerted by a magnet on magnetic materials

definition of weight

the measure of the gravitational force acting on an object

definition of mass

the amount of matter in an object

SI unit of weight

newton (N)

SI unit of mass

kilogram (kg)

how does weight change

may change with location

how does mass change

remains constant regardless of location

measuring instrument for weight

spring balance

measuring instrument for mass

electronic beam balance

effects of forces

change the motion of an object, turning effect, changing size or shape of an object, and changing pressure on an object

pressure

the amount of force acting perpendicularly on a unit area

formula for pressure

pressure (Pa) = force (N) divided by area (m²)

work done

when a force is exerted with energy transferred

formula for work done

work done (J) = constant force (N) x distance moved (m)

formula for weight

weight (N) = mass (kg) x gravitational field strength (N/kg)

kinetic energy

energy found in objects during movement

chemical potential energy

stored energy in substances

gravitational potential energy

energy that is stored in an object due to its postition

electrical energy

energy caused by movement of electrically charged particles

the principal of the conservation of energy

states that energy cannot be created or destroyed and energy can only be changed from one form to another or trannsferred from one object to another

fossil fuels

formed from the remains of dead plants and animals

impacts of using fossil fuels

limited and will run out one day ; releases air pollutants and greenhouse gases that can lead to global warming

solar energy

can be harness with the use of solar panels